The nackCount property of the RTCRtpStreamStats dictionary is a numeric value indicating the number of times the receiver sent a NACK packet to the sender. A NACK (Negative ACKnowledgement, also called "Generic NACK") packet tells the sender that one or more of the RTP packets it sent were lost in transport.


var nackCount = RTCRtpStreamStats.nackCount;


An integer value indicating how many times the receiver sent a NACK packet to the sender after detecting that one or more packets were lost during transport.

Note: This value is only available on the receiver.


Specification Status Comment
Identifiers for WebRTC's Statistics API
The definition of 'RTCRtpStreamStats.nackCount' in that specification.
Candidate Recommendation Initial definition.

Browser compatibility

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ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
nackCountChrome No support NoEdge ? Firefox Full support 55IE No support NoOpera No support NoSafari ? WebView Android No support NoChrome Android No support NoFirefox Android Full support 55Opera Android No support NoSafari iOS ? Samsung Internet Android ?


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Compatibility unknown